AP Biology- Lac/Trp Quiz
Which of the following is not true for activators?
Activators bind directly to the DNA.
The lac repressor
Binds to the operator and prevents transcription
(T/F) In the presence of tryptophan, transcription of the trp operon is on.
False
(T/F) In the presence of tryptophan, transcription of trp operon is on.
False
(T/F) When both glucose and lactose are absent, transcription occurs.
False
The trp operon consists of __________ structural genes.
Five
The trp operon consists of________genes that encode tryptophan biosynthesis enzymes.
Five
In the absence of tryptophan, the trp repressor is
Inactive and cannot bind to the operator
When both glucose and lactose are present
Transcription if turned off
(T/F) An operon is a group of genes that is under the control of a singe operator site.
True
(T/F) In the absence of glucose, when lactose is present it combines with the repressor, allowing RNA polymerase to carry on transcription.
True
(T/F) Regulation of degradative pathways involving an activator that is activated by an inducer is referred to as positive control.
True
(T/F) Some degradative pathways are regulated by an activator protein. An activator is a regulatory protein that facilitates transcription by binding to DNA.
True
(T/F) The inducer of the lac operon is an isomer of lactose.
True
(T/F) The lac repressor protein is active in the absence of lactose within the cell.
True
(T/F) The polycistronic mRNA is transcribed from the lac operon when lactose is present in the cell.
True
(T/F) The trp repressor is a helix-turn-helix regulator protein.
True
(T/F) When RNA polymerase is bound to the lac promoter sequence, transcription of the lac operon is on.
True
In the absence of lactose, the lac repressor is
active and can bind to the opereator
The lac repressor is inactivated by binding to which of the following?
allolactose
When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon.
cAMP ; switches on
When glucose is present
cyclic AMP is low, CAP does not bind to the activator binding site, and transcription is turned off
The lac operon is expressed when
glucose is low and lactose is present
A repressor protein...
is unable to bind to the DNA molecule and prevent transcription
When a microorganism such as E. coli is grown on glucose...
it is capable of amino acid production
The lac repressor binds to what site within the lac operon?
lacO
Which of the following is not part of the lac operon?
lacl
In the presence of tryptophan, tryptophan binds to the
trp repressor
